LATERAL LUXATION OF THE PATELLA 105 



evident that as the general condition of the animal improves, the 

 tendency to recurrence of the luxation will diminish, consequently 

 good feeding and little exertion are indicated. 



In some cases, however, the patella becomes fixed on the superior 

 surface of the inner lip of the trochlea and remains in that position. 

 In this case all the joints of the limb become rigidly extended and 

 the animal is unable to flex them. Occasionally such a luxation 

 n^ay be reduced by causing the animal to make a sudden start, when 

 the patella will descend with a snap. Most frequently, however, 

 manual interference is necessary. If the sharp inferior border of 

 the patella be raised from the flat superior surface of the trochlear 

 ridge, descent of the patella is not difiicult. The method of reduc- 

 tion was recommended by Meyer, who lifted the patella whilst the 

 animal was simultaneously led forwards, thus allowing the patellar 

 border to escape the angle of the trochlea, whilst the contraction of 

 the flexor muscles caused the patella to be pulled downwards through 

 the medium of the straight ligaments. 



LATERAL LUXATION OF THE PATELLA 



Again referring to the conformation of the trochlea, and to the 

 articular surface of the patella, it will be seen that lateral displacement 

 of the patella in the outward direction is not a difficult matter owing 

 to the slight degree of prominence presented by the outer lip of the 

 trochlea. Again considering the progress of the extraordinary degree 

 of extension of the stifle if the tension on the internal lateral patellar 

 hgament should be so great as to cause the ligament to be stretched 

 (or, in rare cases, even ruptured), instead of fixation of the patella on 

 the superior surface of the inner lip as already described, there will be 

 nothing to prevent the patella from shpping off" the trochlea over its 

 outer hp, and this is what in reality occurs. 



